GNU Radio 2.x: gri_iir.h Source File

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# gri_iir.h

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    00001 /* -*- c++ -*- */
    00002 /*
    00003  * Copyright 2002 Free Software Foundation, Inc.
    00004  *
    00005  * This file is part of GNU Radio
    00006  *
    00007  * GNU Radio is free software; you can redistribute it and/or modify
    00008  * it under the terms of the GNU General Public License as published by
    00009  * the Free Software Foundation; either version 2, or (at your option)
    00010  * any later version.
    00011  *
    00012  * GNU Radio is distributed in the hope that it will be useful,
    00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
    00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00015  * GNU General Public License for more details.
    00016  *
    00017  * You should have received a copy of the GNU General Public License
    00018  * along with GNU Radio; see the file COPYING.  If not, write to
    00019  * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
    00020  * Boston, MA 02111-1307, USA.
    00021  */
    00022
    00023 #ifndef INCLUDED_GRI_IIR_H
    00024 #define INCLUDED_GRI_IIR_H
    00025
    00026 #include <vector>
    00027 #include <stdexcept>
    00028
    00032 template<class i_type, class o_type, class tap_type>
    00033 class gri_iir {
    00034 public:
    00058   gri_iir (const std::vector<tap_type>& fftaps,
    00059           const std::vector<tap_type>& fbtaps) throw (std::invalid_argument)
    00060   {
    00061     set_taps (fftaps, fbtaps);
    00062   }
    00063
    00064   gri_iir () : d_latest(0) { }
    00065
    00066   ~gri_iir () {}
    00067
    00072   o_type filter (const i_type input);
    00073
    00078   void filter_n (o_type output[], const i_type input[], long n);
    00079
    00083   unsigned ntaps () const { return d_fftaps.size (); }
    00084
    00088   void set_taps (const std::vector<tap_type> &fftaps,
    00089                  const std::vector<tap_type> &fbtaps) throw (std::invalid_argument)
    00090   {
    00091     if (fftaps.size () != fbtaps.size ())
    00092       throw std::invalid_argument ("gri_iir::set_taps");
    00093
    00094     d_latest = 0;
    00095     d_fftaps = fftaps;
    00096     d_fbtaps = fbtaps;
    00097
    00098     int n = fftaps.size ();
    00099     d_prev_input.resize (2 * n);
    00100     d_prev_output.resize (2 * n);
    00101
    00102     for (int i = 0; i < 2 * n; i++){
    00103       d_prev_input[i] = 0;
    00104       d_prev_output[i] = 0;
    00105     }
    00106   }
    00107
    00108 protected:
    00109   std::vector<tap_type> d_fftaps;
    00110   std::vector<tap_type> d_fbtaps;
    00111   int                   d_latest;
    00112   std::vector<tap_type> d_prev_output;
    00113   std::vector<i_type>   d_prev_input;
    00114 };
    00115
    00116
    00117 //
    00118 // general case.  We may want to specialize this
    00119 //
    00120 template<class i_type, class o_type, class tap_type>
    00121 o_type
    00122 gri_iir<i_type, o_type, tap_type>::filter (const i_type input)
    00123 {
    00124   tap_type      acc;
    00125   unsigned      i = 0;
    00126   unsigned      n = ntaps ();
    00127
    00128   if (n == 0)
    00129     return (o_type) 0;
    00130
    00131   int latest = d_latest;
    00132
    00133   acc = d_fftaps[0] * input;
    00134   for (i = 1; i < n; i ++)
    00135     acc += (d_fftaps[i] * d_prev_input[latest + i]
    00136             + d_fbtaps[i] * d_prev_output[latest + i]);
    00137
    00138   // store the values twice to avoid having to handle wrap-around in the loop
    00139   d_prev_output[latest] = acc;
    00140   d_prev_output[latest+n] = acc;
    00141   d_prev_input[latest] = input;
    00142   d_prev_input[latest+n] = input;
    00143
    00144   latest--;
    00145   if (latest < 0)
    00146     latest += n;
    00147
    00148   d_latest = latest;
    00149   return (o_type) acc;
    00150 }
    00151
    00152
    00153 template<class i_type, class o_type, class tap_type>
    00154 void
    00155 gri_iir<i_type, o_type, tap_type>::filter_n (o_type output[],
    00156                                              const i_type input[],
    00157                                              long n)
    00158 {
    00159   for (int i = 0; i < n; i++)
    00160     output[i] = filter (input[i]);
    00161 }
    00162
    00163 #endif /* INCLUDED_GRI_IIR_H */
    00164